Roads to objectivity: Quantum Darwinism, Spectrum Broadcast Structures, and Strong quantum Darwinism -- a review

TL;DR

This review compares three approaches—quantum Darwinism, Spectrum Broadcast Structures, and strong quantum Darwinism—that explain the emergence of objective classical reality from quantum mechanics, analyzing their foundations and interrelations.

Contribution

It provides a synthetic analysis of three key approaches to quantum objectivity and proves a generalized Spectrum Broadcast Structure theorem.

Findings

Comparison of three approaches to quantum objectivity

Analysis of how each approach realizes objectivity

Proof of a generalized Spectrum Broadcast Structure theorem

Abstract

The problem of objectivity, i.e. how to explain on quantum grounds the objective character of the macroscopic world, is one of the aspects of the celebrated quantum-to-classical transition. Initiated by W. H. Zurek and collaborators, this problem gained some attention recently with several approaches being developed. The aim of this work is to compare three of them: quantum Darwinism, Spectrum Broadcast Structures, and strong quantum Darwinism. The paper is concentrated on foundations, providing a synthetic analysis of how the three approaches realize the idea of objectivity and how they are related to each other. As a byproduct of this analysis, a proof of a generalized Spectrum Broadcast Structure theorem is presented. Recent quantum Darwinism experiments are also briefly discussed.